The fact that you can see information in the prolog of a macro has no bearing on whether it is a documented progarmming interface. Officially, only the books are the arbiter of programming interfaces.
Further, the prolog shows that this Use2Gto32G is not a programming interface: *01* EXTERNAL CLASSIFICATION: * *02* GUPI: BASE * *02* NONE: FIELDS * DOAUTHCHECKS * USE2GTO32G * *01* END OF EXTERNAL CLASSIFICATION: I readily grant that the books are too often wrong. But that does not lessen their official-ness. Help us to get them right. Peter Relson z/OS Core Technology Design
